Until now, as the method for producing an oxidized cyclic phenol sulfide, it is known that there is the method which comprises the step of oxidizing a corresponding cyclic phenol sulfide. Examples of oxidizing agents used for oxidation reaction include hydrogen peroxide, organic peroxides, peracids, halogen oxides, N-halogen compounds, halogen molecules, oxygen, ozone, a nitric acid, and inorganic oxides. Hydrogen peroxide, halogen molecules, and inorganic oxides such as sodium perborate are preferable among them. Though a preferable solvent varies depending on the kind of an oxidizing agent, it is proposed to use halogenated hydrocarbon solvents such as chloroform and dichloromethane; alcohols such as methanol and ethanol; acetonitrile; polar solvents such as an acetic acid and water, and the like. Further, it is also known that, if necessary, catalysts such as vanadium (V) oxide, sodium metavanadate (V), titanium trichloride, tungsten (VI) oxide and sodium phosphate can be used in oxidation reaction.
Thus, various combinations of an oxidizing agent/a solvent/a catalyst are proposed to be used in oxidation of sulfide bond of a cyclic phenol sulfide of formula (A) (refer to Patent Literature 1, for example):
wherein X represents a hydrogen atom, a hydrocarbon group, or an acyl group; Y represents a hydrogen atom, a hydrocarbon group, a halogenated hydrocarbon group, —COR1, —OR2, —COOR3, —CN, —CONH2, —NO2, —NR4R5, a halogen atom, —SO4R6, or —SO3R7, in which R1, R2, R3, R4, R5, R6, and R7 each represents a hydrogen atom or a hydrocarbon group; and 1 represents an integer of 4 to 12. However, the literature discloses that 10 to 50 mL of a solvent is preferably used per 1 g of a cyclic phenol sulfide, which is rather a large quantity of a solvent; that the reaction temperature is preferably 15 to 65° C. when using an inorganic oxide, which is rather a mild range of the embodiment; and that the reaction is conducted for over 2 days until oxidation to a sulfonyl group is completed, which is a long period of time. Further, it discloses that phenolate substituent X is a hydrogen atom, a hydrocarbon group or an acyl group. However, since a compound wherein X is a hydrogen atom is applied to a metal capture agent, purity of an oxidized compound wherein X is a hydrogen atom is not paid attention to. Practically, widely used is the method which comprises the step of oxidizing a cyclic phenol sulfide with sodium perborate or hydrogen peroxide in a halogenated hydrocarbon solvent(s) such as chloroform and in the presence of an acetic acid (refer to Non-patent Literatures 1 to 3, for example).
The reason why a halogenated hydrocarbon solvent is widely used is that though the cyclic phenol sulfide of the formula (A) is poorly soluble in most solvents, it is relatively well soluble in a halogenated hydrocarbon solvent such as chloroform as compared to other solvents. In addition to it, when using ketone, ester, or ether solvents as well as proposed alcohol solvents in the presence of an oxidizing agent, there are risks such as explosion and fire derived from the peroxide production of a solvent itself. This is also the reason why a halogenated hydrocarbon solvent such as chloroform is widely used. Thus, though a halogenated hydrocarbon solvent is practically widely used in oxidation of the cyclic phenol sulfide of the formula (A), usage thereof seriously damages the environment as is well known. Therefore, it would be difficult from both the cost and environmental aspects that a halogenated hydrocarbon solvent is applied on industrial scale where the usage amount thereof becomes large.
Meanwhile, an oxidized cyclic phenol sulfide obtained by oxidizing the cyclic phenol sulfide of the formula (A) is actively studied as a substance which has a variety of possible industrial applicability such as a third-generation inclusion molecule and a static charge control agent which is studied by the present inventors.
However, it is still impossible to develop the environmentally conscious and highly productive production method thereof which is applicable on industrial scale, and the compound is hardly industrially applicable. In order to promote wide use of such a useful substance on the industrial field, it has been eagerly desired to develop the production method thereof which is industrially applicable.
Patent Literature 1: WO98/09959
Non-patent Literature 1: TETRAHEDRON LETTERS 39 (1998) 7559-7562
Non-patent Literature 2: TETRAHEDRON 57 (2001) 5557-5563
Non-patent Literature 3: J. CHEM. SOC., CHEM. COMMUN., 1998, 1345